(function (window) {

  var Game = {

    init: function () {
      this.c = document.getElementById("game");
      this.c.width = this.c.width;
      this.c.height = this.c.height;
      this.ctx = this.c.getContext("2d");
      this.color = "rgba(20,20,20,.7)";
      this.bullets = [];//子弹
      this.enemyBullets = [];//敌方子弹
      this.enemies = [];//敌机
      this.particles = [];//颗粒
      this.bulletIndex = 0;
      this.enemyBulletIndex = 0;
      this.enemyIndex = 0;
      this.particleIndex = 0;
      this.maxParticles = 10;
      this.maxEnemies = 6;
      this.enemiesAlive = 0;//存活敌机
      this.currentFrame = 0;//当前帧
      this.maxLives = 3;//最大三次机会
      this.life = 0;
      this.binding();//键盘按键方法
      this.player = new Player();//new一个玩家
      this.score = 0;
      this.paused = false;//暂停
      this.shooting = false;
      this.oneShot = false;
      this.isGameOver = false;
      //请求动画帧
      this.requestAnimationFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
      for (var i = 0; i < this.maxEnemies; i++) {
        new Enemy();
        this.enemiesAlive++;
      }
      this.invincibleMode(2000);//无敌模式

      this.loop();//重新开始
    },

    binding: function () {
      window.addEventListener("keydown", this.buttonDown);
      window.addEventListener("keyup", this.buttonUp);
      window.addEventListener("keypress", this.keyPressed);
      this.c.addEventListener("click", this.clicked);
    },

    clicked: function () {
      if (!Game.paused) {
        Game.pause();
      } else {
        if (Game.isGameOver) {
          Game.init();//初始化
        } else {
          Game.unPause();//取消暂停
          Game.loop();//重新开始
          Game.invincibleMode(1000);//无敌1秒
        }
      }
    },
    //按下键盘触发
    keyPressed: function (e) {
      if (e.keyCode === 32) {//空格
        if (!Game.player.invincible && !Game.oneShot) {
          Game.player.shoot();
          Game.oneShot = true;//射击
        }
        if (Game.isGameOver) {
          Game.init();
        }
        e.preventDefault();//取消默认行为
      }
    },
    //keyup键盘松开触发
    buttonUp: function (e) {
      if (e.keyCode === 32) {
        Game.shooting = false;
        Game.oneShot = false;
        e.preventDefault();
      }
      if (e.keyCode === 37 || e.keyCode === 65) {//左箭头或A
        Game.player.movingLeft = false;//停
      }
      if (e.keyCode === 39 || e.keyCode === 68) {//右箭头或D
        Game.player.movingRight = false;
      }
    },
    //keydown按下键盘触发
    buttonDown: function (e) {
      if (e.keyCode === 32) {
        Game.shooting = true;
      }
      if (e.keyCode === 37 || e.keyCode === 65) {
        Game.player.movingLeft = true;//开始
      }
      if (e.keyCode === 39 || e.keyCode === 68) {
        Game.player.movingRight = true;
      }
    },

    random: function (min, max) {//生成随机整数
      return Math.floor(Math.random() * (max - min) + min);
    },

    invincibleMode: function (s){//参数
      this.player.invincible = true;
      setTimeout(function () {
        Game.player.invincible = false;
      }, s);
    },
    //击中位置范围
    collision: function (a, b) {
      return !(
        ((a.y + a.height) < (b.y)) ||
        (a.y > (b.y + b.height)) ||
        ((a.x + a.width) < b.x) ||
        (a.x > (b.x + b.width))
      )
    },
    //画布清空
    clear: function () {
      this.ctx.fillStyle = Game.color;
      this.ctx.fillRect(0, 0, this.c.width, this.c.height);
    },

    pause: function () {
      this.paused = true;
    },

    unPause: function () {
      this.paused = false;
    },


    gameOver: function () {
      this.isGameOver = true;
      this.clear();
      var message = "游戏结束";
      var message2 = "得分" + Game.score;
      var message3 = "点击或者空格重新开始";
      this.pause();
      this.ctx.fillStyle = "white";
      this.ctx.font = "bold 30px Lato, sans-serif";
      this.ctx.fillText(message, this.c.width / 2 - this.ctx.measureText(message).width / 2, this.c.height / 2 - 50);
      this.ctx.fillText(message2, this.c.width / 2 - this.ctx.measureText(message2).width / 2, this.c.height / 2 - 5);
      this.ctx.font = "bold 16px Lato, sans-serif";
      this.ctx.fillText(message3, this.c.width / 2 - this.ctx.measureText(message3).width / 2, this.c.height / 2 + 30);
    },
    //更新得分
    updateScore: function () {
      this.ctx.fillStyle = "white";
      this.ctx.font = "16px Lato, sans-serif";
      this.ctx.fillText("Score: " + this.score, 8, 20);
      this.ctx.fillText("Lives: " + (this.maxLives - this.life), 8, 40);
    },

    loop: function () {
      if (!Game.paused) {
        Game.clear();
        for (var i in Game.enemies) {
          var currentEnemy = Game.enemies[i];
          currentEnemy.draw();
          currentEnemy.update();
          if (Game.currentFrame % currentEnemy.shootingSpeed === 0) {
            currentEnemy.shoot();//当前帧更新完后开始射击
          }
        }
        for (var x in Game.enemyBullets) {
          Game.enemyBullets[x].draw();
          Game.enemyBullets[x].update();
        }
        for (var z in Game.bullets) {
          Game.bullets[z].draw();
          Game.bullets[z].update();
        }
        if (Game.player.invincible) {
          if (Game.currentFrame % 20 === 0) {
            Game.player.draw();//无敌时间后开始绘制玩家
          }
        } else {
          Game.player.draw();
        }

        for (var i in Game.particles) {
          Game.particles[i].draw();
        }
        Game.player.update();
        Game.updateScore();
        Game.currentFrame = Game.requestAnimationFrame.call(window, Game.loop);
      }
    }

  };

  var Player = function () {//var玩家一些属性方法
    this.width = 60;
    this.height = 20;
    this.x = Game.c.width / 2 - this.width / 2;
    this.y = Game.c.height - this.height;
    this.movingLeft = false;
    this.movingRight = false;
    this.speed = 8;
    this.invincible = false;
    this.color = "white";
  };


  Player.prototype.die = function () {//构造函数 死
    if (Game.life < Game.maxLives) {
      Game.invincibleMode(2000);
      Game.life++;
    } else {
      Game.pause();
      Game.gameOver();
    }
  };


  Player.prototype.draw = function () {//再画一遍
    Game.ctx.fillStyle = this.color;
    Game.ctx.fillRect(this.x, this.y, this.width, this.height);
  };


  Player.prototype.update = function () {
    if (this.movingLeft && this.x > 0) {
      this.x -= this.speed;
    }
    if (this.movingRight && this.x + this.width < Game.c.width) {
      this.x += this.speed;
    }
    if (Game.shooting && Game.currentFrame % 10 === 0) {
      this.shoot();
    }
    for (var i in Game.enemyBullets) {
      var currentBullet = Game.enemyBullets[i];
      if (Game.collision(currentBullet, this) && !Game.player.invincible) {
        this.die();//在不是玩家无敌时，玩家和敌机子弹位置范围接触
        delete Game.enemyBullets[i];
      }
    }
  };


  Player.prototype.shoot = function () {
    Game.bullets[Game.bulletIndex] = new Bullet(this.x + this.width / 2);
    Game.bulletIndex++;
  };

  var Bullet = function (x) {
    this.width = 8;
    this.height = 20;
    this.x = x;
    this.y = Game.c.height - 10;
    this.vy = 8;
    this.index = Game.bulletIndex;
    this.active = true;
    this.color = "white";

  };

  Bullet.prototype.draw = function () {
    Game.ctx.fillStyle = this.color;
    Game.ctx.fillRect(this.x, this.y, this.width, this.height);
  };


  Bullet.prototype.update = function () {
    this.y -= this.vy;
    if (this.y < 0) {
      delete Game.bullets[this.index];
    }
  };

  var Enemy = function () {
    this.width = 60;
    this.height = 20;
    this.x = Game.random(0, (Game.c.width - this.width));
    this.y = Game.random(10, 40);
    this.vy = Game.random(1, 3) * .1;
    this.index = Game.enemyIndex;
    Game.enemies[Game.enemyIndex] = this;
    Game.enemyIndex++;
    this.speed = Game.random(2, 3);
    this.shootingSpeed = Game.random(30, 80);
    this.movingLeft = Math.random() < 0.5 ? true : false;
    this.color = "hsl(" + Game.random(0, 360) + ", 60%, 50%)";

  }

  Enemy.prototype.draw = function () {
    Game.ctx.fillStyle = this.color;
    Game.ctx.fillRect(this.x, this.y, this.width, this.height);
  };

  Enemy.prototype.update = function () {
    if (this.movingLeft) {
      if (this.x > 0) {
        this.x -= this.speed;
        this.y += this.vy;
      } else {
        this.movingLeft = false;
      }
    } else {
      if (this.x + this.width < Game.c.width) {
        this.x += this.speed;
        this.y += this.vy;
      } else {
        this.movingLeft = true;
      }
    }

    for (var i in Game.bullets) {
      var currentBullet = Game.bullets[i];
      if (Game.collision(currentBullet, this)) {
        this.die();//敌机死
        delete Game.bullets[i];
      }
    }
  };

  Enemy.prototype.die = function () {
    this.explode();//敌机死后爆炸
    delete Game.enemies[this.index];
    Game.score += 15;//击落一个计分15
    Game.enemiesAlive = Game.enemiesAlive > 1 ? Game.enemiesAlive - 1 : 0;
    if (Game.enemiesAlive < Game.maxEnemies) {
      Game.enemiesAlive++;//敌机数
      setTimeout(function () {
        new Enemy();
      }, 2000);//2秒新增一个敌机
    }

  };

  Enemy.prototype.explode = function () {//爆炸
    for (var i = 0; i < Game.maxParticles; i++) {
      new Particle(this.x + this.width / 2, this.y, this.color);
    }
  };

  Enemy.prototype.shoot = function () {
    new EnemyBullet(this.x + this.width / 2, this.y, this.color);
  };

  var EnemyBullet = function (x, y, color) {
    this.width = 8;
    this.height = 20;
    this.x = x;
    this.y = y;
    this.vy = 6;
    this.color = color;
    this.index = Game.enemyBulletIndex;
    Game.enemyBullets[Game.enemyBulletIndex] = this;
    Game.enemyBulletIndex++;
  };

  EnemyBullet.prototype.draw = function () {
    Game.ctx.fillStyle = this.color;
    Game.ctx.fillRect(this.x, this.y, this.width, this.height);
  };

  EnemyBullet.prototype.update = function () {
    this.y += this.vy;
    if (this.y > Game.c.height) {
      delete Game.enemyBullets[this.index];
    }
  };

  var Particle = function (x, y, color) {
    this.x = x;
    this.y = y;
    this.vx = Game.random(-5, 5);
    this.vy = Game.random(-5, 5);
    this.color = color || "orange";
    Game.particles[Game.particleIndex] = this;
    this.id = Game.particleIndex;
    Game.particleIndex++;
    this.life = 0;
    this.gravity = .05;
    this.size = 40;
    this.maxlife = 100;
  }

  Particle.prototype.draw = function () {
    this.x += this.vx;
    this.y += this.vy;
    this.vy += this.gravity;
    this.size *= .89;
    Game.ctx.fillStyle = this.color;
    Game.ctx.fillRect(this.x, this.y, this.size, this.size);
    this.life++;
    if (this.life >= this.maxlife) {
      delete Game.particles[this.id];
    }
  };

  Game.init();

}(window));